John henneman



UNITED STATES PATENT QFFICE.

JOHN HENNEMAN, OF CHICAGO, ILLINOIS, ASSIGNOR OF ONE-HALF TO RICHARD E.STUPE, OF SAME PLACE.

ENAMEL FOR COATING SHEET METAL, 800.

SPECIFICATION forming part of Letters Patent No. 517,454, dated April 3,18941. Application filed April 1,1893. SerialN'o. 468,717. (Nospecimens.)

To all whom it may concern:

Be it known that I, JOHN I-IENNEMAN, a citizen of the United States ofAmerica, residing at Chicago, county of Cook, State of Illinois, haveinvented certain new and useful Improvements in Enamel for Coating SheetMetal and other Metals, of which the following is a description.

It is well known that vitreous enamel, such as is usually applied tometal, is a substance similar to and .partakes of the known qualities ofglass. Hence it has not been practicable to enamel other than stiff,inflexible articles, such as culinary utensils, and similar articles, asthe bending of a flexible article results in cracking off the enamel. Ithas also been found necessary in practicing the known processes ofenameling, to first prepare the metal by a preparatory coat of somekind, such, for example, as by a coat of enamel composed of white-sand,mica, and borax, after which one or more coats of finishing enamel isadded.

I have discovered a process of enameling metal articles whereby theenamel produced upon said articles is flexible, and the articlesenameled can be bent more or less without cracking or injuring itsenameled surface; and whereby, in the manufacture of the enameledarticle, the preparatory coating, above referred to, may be dispensedwith, and the entire work performed by one heat, thereby very largelyreducing the cost of manufacture.

My improved process is substantially as follows: I use the followingarticles in substantially the following proportions, to-wit: Floor-spar,two and one-half pounds; saltpeter, one and one-half pounds; white-sand,five pounds; pulverized-borax, four pounds; mica, two pounds; red lead,three pounds; carbonate of potash, three pounds; kryolite, two

pounds, together with a small quantity of coloring oxide, for example,for a blue color onehalf ounce of oxide of cobalt.

The above ingredients are mixed and milled in the usual manner,preferably being milled wet. The mixture is applied to the metal bypouring or dipping and allowed to dry to prevent the formation ofblisters or holes in the enamel. The enameled article is then placed inan oven or furnace heated to from 1,000 to 1,500 Fahrenheit, and bakeduntil the application of the enamel is complete. In practice, after theenamel has fused, I prefer to cool the enameled metal slowly, and forthis purpose to pass it from the fusing furnace through a series ofchambers, each of which is of a lower temperature than the precedingone.

Of course the metal may be subjected to the usual preparatory coat, ifpreferred, but ordinarily the enameling coating above described issufficient, and the expense of a preparatory heating and coating isthereby avoided.

Articles enameled by the above described process may be bent or flexedwithout cracking or scaling the enamel. Hence, this process isparticularly adapted to sheet-metal roofing and other flexiblesheet-metal articles.

Having thus described my improved process, what I claim as new, anddesire to secure by Letters Patent, is-

An enamel composed of a mixture of fluorspar, salt-peter, white-sand,borax, mica, redlead, carbonate of potash, and kryolite with 2.sptiltable coloring oxide, substantially as set JOHN W. HILL, W. M.HILL.

